Balancing device for internal combustion engine

Abstract

The present invention is provided with: an idler shaft (28) having an idler sprocket (30) around which a drive chain (25) is wound, and an idler gear (31) integrated with the idler sprocket; a balance housing (11) that accommodates therein a balance shaft that generates a starting force by the rotational force transmitted from the idle gear; the present invention is provided with: a support section (22) which is disposed on the outer side of an upper housing (17) and supports the end of an idler shaft; a boss portion (21) provided close to the support portion in the same row in the longitudinal direction; and a first reinforcing part (37) and a second reinforcing part (38) which are arranged between the supporting part and the boss part and reinforce the lower part of the lower housing (16) side of the supporting part. This makes it possible to suppress the occurrence of abnormal noise and vibration between the idler gear and the drive-side gear.

Description

Technical Field

[0001] The present invention relates to a balancing device for reducing secondary vibration of an internal combustion engine. Background Art

[0002] As a conventional balancing device for an internal combustion engine, there is a balancing device described in the following Patent Document 1. Briefly described, the balancing device comprises: a housing mounted on the lower portion of a crankcase of the internal combustion engine and housed in an oil pan; a driving side balancing shaft housed and supported to be rotatable via a pair of sliding bearings arranged at a predetermined interval in the axial direction of the housing, and transmitting a rotational force from the crankshaft; and a driven side balancing shaft housed and supported to be rotatable via a pair of sliding bearings arranged at a predetermined interval in the axial direction of the housing, and transmitting a rotational force from the driving side balancing shaft.

[0003] The driving side balance shaft transmits the rotational force from the crankshaft via a driving chain wound around a driving side sprocket at the front end. In addition, a pair of counterweights are provided on the driving side balance shaft.

[0004] The driven side balance shaft transmits rotational force from a driving gear provided on the driving side balance shaft via a driven gear. In addition, a pair of counterweights are also integrally provided on the driven side balance shaft.

[0005] When the crankshaft is driven to rotate by starting the internal combustion engine, the driving side balance shaft is driven to rotate at twice the rotation speed of the crankshaft via the driving side sprocket of the driving side balance shaft wound on the drive chain, and the driven side gear meshing with the driving side gear rotates in the opposite direction, thereby driving the driven side balance shaft to rotate in the opposite direction to the driving side balance shaft. Thus, the secondary vibration of the internal combustion engine is effectively suppressed by the rotation of each counterweight.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: (Japanese) Patent Publication No. 2008-14351 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] However, in the above-mentioned balancing device, as a transmission mechanism for transmitting the rotational force of the crankshaft to the driving side balance shaft, in addition to the method of directly transmitting to the driving side balance shaft via the drive chain as described above, there is also a mechanism that uses an idler shaft set on the side of the driving side balance shaft.

[0011] According to the layout of each component, a support portion is integrally provided on the outer side of the housing, and the idler shaft is axially supported on the support portion. The idler shaft has an idler sprocket around which a drive chain is wound, and an idler gear integrally provided with the idler sprocket and meshing with the drive side gear. An idler driven gear meshing with the idler gear is provided at the front end of the drive side balance shaft. The rotational force of the crankshaft is transmitted from the drive chain to the drive side balance shaft via the idler sprocket, the idler gear, and the idler driven gear.

[0012] However, in the transmission mechanism using the idler shaft, a large tensile force (tension) in the crankshaft direction caused by the drive chain acts on the idler shaft via the idler sprocket.

[0013] Through analysis, it is clear that due to the large tensile force, the support part supporting the idler shaft is deformed, the idler shaft is prone to tilting toward the crankshaft, and there is a possibility of misalignment between the idler gear and the idler driven gear. As a result, meshing noise and vibration are generated between the idler gear and the driving side gear, and uneven wear may occur between the two gears over time.

[0014] The present invention is proposed in view of the technical problems of the above-mentioned previous balancing devices, and one of its purposes is to provide a balancing device for an internal combustion engine, which suppresses the tipping of the idler shaft by increasing the rigidity of the supporting part and reduces the misalignment between the idler gear and the driving side gear, thereby being able to suppress the occurrence of abnormal noise and vibration.

[0015] Technical solutions for solving technical problems

[0016] The invention described in claim 1 is characterized in that:

[0017] The balance housing comprises: an upper housing; a lower housing, which is arranged at the lower part of the upper housing and accommodates a pair of balance shafts in a space formed between the lower housing and the upper housing; a support portion, which is provided at a position of the upper housing that is closer to the outside than the fastening surface of the upper housing and the lower housing and supports an end portion of the idler shaft that is on the opposite side of the idler sprocket in the axial direction; a fixing portion, which is provided on the upper housing in the same row as the supporting portion in the length direction and has a mounting surface that abuts against the lower part of the internal combustion engine; and a first thick-walled portion, which is arranged in a manner to connect the supporting portion and the fixing portion and reinforces the lower part of the lower housing side of the supporting portion.

[0018] Effects of the Invention

[0019] According to the present invention, the occurrence of abnormal noise and vibration can be suppressed by reducing the positional deviation between the idler gear and the driving side gear. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a front view of the main parts showing a state in which one embodiment of the balancing device of the present invention is mounted on an internal combustion engine.

[0021] Figure 2 It is a top view of the balancing device according to this embodiment.

[0022] Figure 3 It is a bottom view of the balancing device according to this embodiment.

[0023] Figure 4 It is a side view of the balancing device according to this embodiment.

[0024] Figure 5 It is a perspective view showing the main part of the balancing device according to the present embodiment.

[0025] Figure 6 yes Figure 2 A-A line cross-sectional view.

[0026] Figure 7 is from Figure 2 Stereoscopic image cut along the B-B line.

[0027] Figure 8 is from Figure 2 Stereoscopic image cut along the C-C line.

[0028] Fig. 9 is from Figure 2 Stereoscopic image cut along the D-D line.

[0029] Fig.10 is from Figure 2 Stereoscopic image cut along line E-E. DETAILED DESCRIPTION

[0030] Hereinafter, an embodiment in which the balancing device of the present invention is applied to, for example, an inline four-cylinder internal combustion engine of an automobile will be described with reference to the drawings.

[0031] [First embodiment]

[0032] Figure 1 1 is a front view of the main parts showing a state where one embodiment of the balancing device of the present invention is mounted on an internal combustion engine. Figure 2 is a top view of the balancing device of this embodiment, Figure 3 is a bottom view of the balancing device of this embodiment, Figure 4 It is a side view of the balancing device according to this embodiment.

[0033] like Figure 1 As shown, a bearing cap 4 having a bearing portion for axially supporting a crankshaft 3 is fixed to the lower portion of a cylinder block 2 of an internal combustion engine 1 , and an oil pan (not shown) having a vertical division and storing engine oil therein is mounted below the bearing cap 4 .

[0034] The crankshaft 3 is rotatably supported at the bottom of the cylinder block 2 by a plurality of bearings including bearing caps connected by bearing bolts, and a large-diameter crankshaft sprocket 6 is mounted on a shaft end 3a integrally provided at the front end side.

[0035] The crank sprocket 6 is joined to the shaft end portion 3 a of the crankshaft 3 by shrink fitting via an insertion hole 6 a formed in the center portion.

[0036] A balance device 10 for suppressing secondary vibration of the internal combustion engine is accommodated and arranged in a space surrounded by the lower portion of the cylinder block 2, the bearing cap 4, and the oil pan.

[0037] like Figure 1 to Figure 4 As shown, the balancing device 10 comprises: a balancing housing 11, which is fixed to the lower surface of the cylinder block 2; a driving side balancing shaft 12 and a driven side balancing shaft 13, which are rotatably supported in a space portion 11a provided inside the balancing housing 11 and are arranged in parallel along the front-rear direction of the internal combustion engine; a helical driving side gear 14 and a driven side gear 15, whose teeth are meshed with each other, and which are respectively arranged on the sides of the approximately central portions of the two balancing shafts 12 and 13.

[0038] The balance housing 11 is composed of a lower housing 16 on the oil pan side and an upper housing 17 disposed on the upper portion of the lower housing 16 .

[0039] The two housings 16 and 17 are formed of aluminum material for light weight, and are fastened and fixed from the top and bottom by a plurality of fastening bolts 18 .

[0040] For the above-mentioned lower shell 16 and upper shell 17, frame-shaped plate portions 19a, 19b of a specified width are formed on the outer periphery of the joint portions opposite to each other from top to bottom, and three parallel first to third cross beam plate portions 20a, 20b, 20c for bearings connected in a manner of crossing the above-mentioned frame-shaped plate portions 19, 20 are integrally formed.

[0041] A plurality of bosses 21 are integrally formed on both sides of the lower housing 16 and the upper housing 17. The bosses 21 are used to form insertion holes 21a for inserting bolts (not shown) for fixing the balance housing 11 to the cylinder block 2. One of the bosses 21 is a support portion 22 provided on the upper housing 17, which will be described later.

[0042] The upper surface of the lower shell 16 is formed into a flat shape that can abut against the lower surface of the upper shell 17. Figure 3 As shown, the lower housing 16 is formed with bosses 21 ′ at positions corresponding to the bosses 21 of the upper housing 17 , and the bosses 21 ′ are formed with insertion holes 21 a ′ for inserting bolts.

[0043] The upper housing 17 has a flat lower surface and the upper surfaces of the bosses 21 including the support portions 22 are formed into eight mounting surfaces 21b and 22b that abut against the lower surface of the cylinder block 2. The mounting surfaces 21b and 22b are flat surfaces.

[0044] The driving side balance shaft 12 is provided with a helical idler driven gear 23 at the front end shaft portion 12c protruding forward from the balance housing 11. The idler driven gear 23 transmits the rotational force from the crankshaft 3 to the driving side balance shaft 12 via a drive chain 25 wound between a rotation transmission component 24 described later and the crankshaft sprocket 6. As a result, the two balance shafts 12 and 13 rotate in opposite directions to each other via the driving side gear 14 and the driven side gear 15. It should be noted that the two balance shafts 12 and 13 are set to rotate two revolutions for every one revolution of the crankshaft 3. In addition, as Figure 1 As shown, the tension of the drive chain 25 is adjusted by a chain tensioner 35 .

[0045] The distal end shaft portion 12 c is rotatably supported by a half-split bearing portion (not shown) formed between the lower housing 16 and the upper housing 17 , and the bearing portion is vertically fixed by a pair of fastening bolts 18 that fasten the lower housing 16 and the upper housing 17 .

[0046] For the drive side balance shaft 12, Figure 2 As shown, three cylindrical journal surfaces (not shown) are respectively formed on the front end side, the center portion and the rear end side in the axial direction, and two of the journal surfaces are rotatably supported by two sliding bearings (not shown) having first and second bearing grooves (not shown) respectively formed at the positions of the first cross beam plate portion 20a and the third cross beam plate portion 20c of the above-mentioned lower shell 16 and upper shell 17.

[0047] The driving side balance shaft 12 is integrally provided with two semicircular first and second counterweights 12a and 12b at symmetrical positions in front and behind the second beam plate portion 20b. The two counterweights 12a and 12b are formed in substantially the same shape and weight, but are formed at positions offset from each other by a predetermined angle in the circumferential direction.

[0048] The driving side gear 14 is fixed to the driving side balance shaft 12 by press fitting or the like, and is clamped by a thrust wall (not shown) to restrict movement in the axial direction.

[0049] For the driven side balance shaft 13, Figure 2 As shown, its axial length is formed in a manner shorter than that of the driving side balance shaft 12, and journal surfaces (not shown) formed at two axial locations are rotatably supported by two semicircular bearing grooves formed in the first beam plate portion 20a and the third beam plate portion 20c via plane bearings.

[0050] The driven side balance shaft 13 is integrally provided with two first and second semicircular arc-shaped counterweights 13a and 13b at front-rear symmetrical positions sandwiching the second beam plate portion 20b. The two counterweights 13a and 13b are set to have substantially the same shape and the same weight.

[0051] The driven side gear 15 is fixed to the driven side balance shaft 13 by press fitting or the like, and like the driving side gear 14 , is clamped in a groove formed in the lower case 16 , that is, by opposing thrust walls of the groove, and is restricted from moving in the axial direction.

[0052] Figure 5 is a perspective view showing the main parts of the balancing device of this embodiment, Figure 6 yes Figure 2 A-A line section view, Figure 7 is from Figure 2 The three-dimensional image cut along the B-B line. Figure 8 is from Figure 2 The three-dimensional image cut along the C-C line. Fig. 9 is from Figure 2 The three-dimensional image cut along the D-D line. Fig.10 is from Figure 2 Stereoscopic image cut along line E-E.

[0053] Moreover, if Figure 1 and Figure 2 As shown, the upper housing 17 is integrally provided with a support portion 22 for supporting an idler shaft 28 to be described later, at an outer portion of a front end portion.

[0054] like Figure 5 and Fig.10 As shown in FIG. 1 , the support portion 22 is formed of aluminum material in a substantially block shape similarly to the upper housing 17. As described above, the support portion 22 is integrally provided on the outer side of one side portion in the width direction of the frame-shaped plate portion 19 of the upper housing 17 for reasons such as the layout of the components, that is, avoiding the crankshaft 3 located above the balance housing 11, or avoiding interference with the oil pan located below the balance housing 11.

[0055] Furthermore, as described above, the support portion 22 has bolt insertion holes 22 a formed in the inner side of the outer portion along the vertical direction, through which bolts for fixing the balance housing 11 to the cylinder block 2 are inserted from below, and a flat mounting surface 22 b is formed on the upper surface of the support portion 22 .

[0056] The support portion 22 has a through hole 27 extending parallel to the front end shaft portion 12c at a position avoiding the bolt insertion hole 22a therein. A small diameter portion 28a, which is one axial end portion of an idler shaft 28 to be described later, is inserted and supported in the through hole 27.

[0057] like Figure 6 As shown, the idler shaft 28 has: a small diameter portion 28a, which is arranged at one end in the axial direction and inserted into the above-mentioned through hole 27; a large diameter portion 28b, which is arranged at the other end in the axial direction and extends outward from the small diameter portion 28a; and a flange portion 28c, which is arranged at the junction between the small diameter portion 28a and the large diameter portion 28b.

[0058] The small diameter portion 28a has an outer diameter slightly smaller than the inner diameter of the through hole 27 and is inserted into the inner circumference of the through hole 27 in a close contact state. An external thread portion 28d is formed on the outer circumference on the opposite side of the large diameter portion 28b in the axial direction.

[0059] The idler shaft 28 is fixed to the support portion 22 via the flange portion 28 c by the tightening force of the flange nut 29 threadedly engaged with the external thread portion 28 d.

[0060] The large diameter portion 28b is provided with a rotation transmission member 24 on the outer periphery in a freely rotatable manner. The rotation transmission member 24 includes an idler sprocket 30, which is provided on the front end side and is wound around the drive chain 25; and an idler gear 31 with helical teeth, which is provided integrally with the idler sprocket 30 on the rear end side and meshes with the idler driven gear 23. The idler sprocket 30 and the idler gear 31 are separated from each other by a predetermined distance in the axial direction via a circular ring portion 32 provided in the center. In addition, the rotation transmission member 24 is restricted in free axial movement by a disc-shaped restriction plate 33 provided at the front end of the large diameter portion 28b and the flange portion 28c. The restriction plate 33 is fixed to the front end surface of the large diameter portion 28b by a fixing bolt 34, and the fixing bolt 34 is screwed into an internal threaded hole 28e formed inside the front end of the large diameter portion 28b.

[0061] In addition, an oil passage is formed inside the small diameter portion 28a and the large diameter portion 28b, through which lubricating oil for lubricating the large diameter portion 28b and the rotation transmission member 24 flows. Figure 6 As shown, an inlet passage 36 connected to an oil supply passage (not shown) for lubricating the bearing portions of each balance shaft 12, 13 is formed in the axial direction inside the small diameter portion 28a and the large diameter portion 28b, and branch passages 36a, 36b are provided in the large diameter portion 28b for radially branching from the inlet passage 36 and supplying lubricating oil to a cylindrical gap C between the inner circumferential surface of the rotation transmission component 24 and the outer circumferential surface of the large diameter portion 28b.

[0062] Moreover, in the present embodiment, between the support portion 22 and the boss portion 21 connected thereto, the upper shell 17 is provided with a first thick wall portion, i.e., a first reinforcing portion 37, and a second thick wall portion, i.e., a second reinforcing portion 38, which improve the rigidity of the support portion 22. Here, the definition of "thick wall" in the first thick wall portion and the second thick wall portion means thicker than the thinnest portion of the upper shell 17 having a thickness.

[0063] That is, for the first reinforcing portion 37, if Figure 2 , Figure 4 , Figure 5 (shaded area) and Figure 7 to Figure 10 As shown, the first reinforcing portion 37 is formed into a thick-walled substantially rectangular cross-section, one end portion 37a is integrally connected to the lower end portion of the support portion 22, and is formed in a straight line from the one end portion 37a toward the side of the boss portion 21, and the other end portion 37b is connected to the lower end portion of the outer surface of the boss portion 21. In addition, the first reinforcing portion 37 is arranged in parallel with an imaginary line that is perpendicular to the mounting surface 22b of the support portion 22 and passes through the axis of the idler shaft 28.

[0064] Therefore, the first reinforcing portion 37 connects the lower end of the support portion 22 with the lower portion of the boss portion 21. Figure 5 to Figure 7 As shown, the entire portion from one end 37a to the other end 37b protrudes downward from the lower end surface of the support portion 22 by about 6 mm, and protrudes downward compared to the joint surface P between the upper shell 17 and the lower shell 16. The formation position of the one end 37a of the first reinforcement portion 37 is set via the idler shaft 28 in the direction of tension in the direction of the crankshaft 3 caused by the drive chain 25 ( Figure 7 Therefore, the first reinforcing portion 37 improves the rigidity of the supporting portion 22 with respect to the above-mentioned tensile force as described later.

[0065] For the second reinforcement portion 38, Figure 2 , Figure 4 , Figure 5 as well as Figure 7 to Figure 10 As shown, the cross section is formed in a generally irregular shape, and is integrally connected to the upper surface of the first reinforcing portion 37, that is, it is integrally connected to the width direction position of the first reinforcing portion 37 at an upper position, and one end 38a is connected to the approximately central position of the support portion 22 in the vertical direction, and extends from there to the approximately central position of the above-mentioned boss portion 21 in the vertical direction, and the other end 38b is integrally connected to the boss portion 21. In addition, the second reinforcing portion 38 constitutes a part of the upper shell 17, and constitutes a part of the above-mentioned space portion 11a that accommodates the two balance shafts 12 and 13 on the inner side. In addition, as shown Figure 7 As shown, the lower surface 38 c of the second reinforcing portion 38 serves as a joining surface P with the upper surface of the lower case 16 .

[0066] In addition, if Figures 4 to 9 As shown, the first reinforcement portion 37 and the second reinforcement portion 38 are formed in a continuous arc concave shape so that the continuous outer surface 39 on the flange nut 29 side fastened to the idler shaft 28 avoids the flange nut 29 and the periphery of the flange nut 29 .

[0067] [Effects of this embodiment]

[0068] Therefore, according to the balancing device 10, when the internal combustion engine is started and the crankshaft 3 is driven to rotate, the driving side balance shaft 12 is rotated at twice the speed of the crankshaft 3 via the crankshaft sprocket 6, the drive chain 25, the rotation transmission member 24, and the idler driven gear 23. As a result, the driven side balance shaft 13 is rotated at the same speed in the opposite direction to the driving side balance shaft 12 via the meshing rotation transmission between the driving side gear 14 and the driven side gear 15. As a result, the respective counterweights 12a, 12b, 13a, and 13b also rotate in the opposite directions to each other while canceling the left and right centrifugal forces of the balance shafts 12 and 13 themselves.

[0069] At this time, the balancer housing 11 prevents the oil accumulated in the oil pan from interfering with the balancer shafts 12 and 13 , and transmits the vibration force to the internal combustion engine while receiving the vibration force generated when the balancer shafts 12 and 13 rotate.

[0070] In this way, as the balance shafts 12 and 13 rotate, the counterweights 12 a to 13 b rotate to transmit the vibrating force to the internal combustion engine 1 , thereby suppressing the secondary vibration.

[0071] Moreover, in the present embodiment, the lower portion of the support portion 22 that supports the small diameter portion 28a of the idler shaft 28 has its rigidity ensured by the first reinforcement portion 37, so that even if the drive chain 25 applies a large tensile force to the idler sprocket 30 in the direction of the crankshaft 3, the plastic deformation of the support portion 22 can be fully suppressed.

[0072] That is, the inventors of the present invention formed the balancing housing 11 by using an aluminum material (Young's modulus 71 GPa), and when the same chain tension of the drive chain 25 was applied to two supporting parts 22 of the same size via the idler shaft 28, the plastic deformation amount of each supporting part 22 was verified by analysis, with the first reinforcing part 37 being provided and the first reinforcing part 37 being not provided.

[0073] According to this analysis, the amount of plastic deformation of the support portion 22 is about 0.032 mm when the first reinforcing portion 37 is not provided. In contrast, the amount of plastic deformation is about 0.021 mm when the first reinforcing portion 37 is provided. Therefore, according to this experimental result, it can be seen that when the first reinforcing portion 37 is provided, the amount of plastic deformation is reduced by about 0.11 mm compared to when the first reinforcing portion 37 is not provided.

[0074] Therefore, in the present embodiment, by providing the first reinforcement portion 37, as described above, the plastic deformation of the support portion 22 can be sufficiently suppressed, and thus the tilting of the idler shaft 28 can be suppressed. As a result, the misalignment between the idler gear 31 of the rotation transmission member 24 and the idler driven gear 23 of the driving side balance shaft 12 is reduced, and the meshing noise and vibration of the two gears 23 and 31 can be sufficiently suppressed.

[0075] In particular, since the first reinforcing portion 37 is provided integrally with the upper housing 17 , the rigidity of the support portion 22 can be effectively increased, and thus the effect of suppressing the tilting of the idler shaft 28 becomes greater.

[0076] By extending the lower end of the first reinforcing portion 37 downward by, for example, about 6 mm, it is possible to increase the cross-sectional area of ​​the first reinforcing portion 37. This can improve the rigidity of the support portion 22 and increase the effect of suppressing plastic deformation.

[0077] In addition, in the present embodiment, the second reinforcing portion 38 is provided in addition to the first reinforcing portion 37, so that the rigidity of the supporting portion 22 can be further improved, and thus the supporting rigidity of the idler shaft 28 is further improved with respect to the tensile force of the drive chain 25. Therefore, the effect of suppressing the tilting of the idler shaft 28 is further increased, the misalignment between the idler gear 31 and the idler driven gear 23 is reduced, and the effect of suppressing the occurrence of meshing abnormal noise and vibration of the two gears 23 and 31 is further increased.

[0078] In addition, the first reinforcement portion 37 and the second reinforcement portion 38 are arranged at a position avoiding the flange nut 29 used to fix the idler shaft 28. Therefore, the existence of the first and second reinforcement portions 37 and 38 will not affect the outer diameter of the idler shaft 28, and the outer diameter can be made as large as possible.

[0079] Moreover, for the first and second reinforcement parts 37 and 38, the outer surface 39 is formed in an arc shape and is located at a position sufficiently away from the flange nut 29, thereby ensuring an effective operating space for the rotation operating tool of the flange nut 29, such as a wrench, and ensuring the thick wall rigidity as the reinforcement part.

[0080] In the present embodiment, in accordance with the requirement for weight reduction, the balancing housing 11 and the support portion 22 are formed of an aluminum material. As a result, the rigidity of the support portion 22 is lower than when it is formed of cast iron or the like. Therefore, the support portion 22 is easily plastically deformed by the force in the shear direction of the idler shaft 28 due to the tensile force of the drive chain 25. However, since the rigidity of the support portion 22 and the surrounding areas of the support portion 22 can be increased by the first and second reinforcement portions 37 and 38, the balancing housing 11 can be lightweighted and the plastic deformation of the support portion 22 can be sufficiently suppressed.

[0081] Since the first reinforcing portion 37 is provided at a position on the opposite side to the tensile direction of the drive chain 25 with respect to the mounting surface 22b of the support portion 22 to which the upper housing 17 is mounted, the support reaction force to the tensile force on the idler shaft 28 is directly applied by the first reinforcing portion 37. Therefore, the plastic deformation of the support portion 22 can be effectively suppressed.

[0082] Description of Reference Numerals

[0083] 1: Internal combustion engine, 2: Cylinder block, 3: Crankshaft, 4: Bearing cap, 6: Crankshaft sprocket, 10: Balance device, 11: Balance housing, 11a: Storage portion (space portion), 12: Drive side balance shaft, 12a, 12b: First and second balance weights, 12c: Front end shaft, 13: Drive side balance shaft, 13a, 13b: First and second balance weights, 14: Drive side gear, 15: Drive side gear, 16: Lower housing, 17: Upper housing, 21: Boss portion, 22: Support portion, 22a: Bolt insert Entrance hole, 22b: mounting surface, 23: idler driven gear, 24: rotation transmission component, 25: drive chain, 27: through hole, 28: idler shaft, 28a: small diameter portion, 28b: large diameter portion, 28c: flange portion, 29: flange nut, 30: idler sprocket, 31: idler gear, 37: first reinforcement portion (first thick wall portion), 37a: one end portion, 37b: the other end portion, 38: second reinforcement portion (second thick wall portion), 38a: one end portion, 38b: the other end portion, 39: arc concave outer surface.

Claims

1. A balancing device for an internal combustion engine, characterized in that: have: an idler shaft having an idler sprocket around which a drive chain is wound, and an idler gear provided integrally with the idler sprocket; a pair of balancing shafts having balancing weights for generating a vibration-generating force by a rotational force transmitted from the idler gear; a balancing housing that rotatably accommodates the pair of balancing shafts; The balancing housing has: Upper shell; A lower housing, which is disposed at the lower portion of the upper housing and accommodates the two balance shafts in a space formed between the lower housing and the upper housing; a support portion provided at a position of the upper case that is outside the fastening surface between the upper case and the lower case and supports an end portion of the idler shaft that is on the opposite side to the idler sprocket in the axial direction; a fixing portion, which is disposed on the upper housing in the same row as the supporting portion in the length direction and adjacent to the supporting portion, and has a mounting surface that abuts against a lower portion of the internal combustion engine; The first thick wall portion is arranged so as to connect the support portion and the fixing portion, and reinforces a lower portion of the support portion on the lower casing side.

2. The balancing device for an internal combustion engine according to claim 1, characterized in that: The support portion, the fixing portion, and the first thick-walled portion are integrally provided with the upper housing.

3. The balancing device for an internal combustion engine according to claim 2, characterized in that: A second thick wall portion is integrally connected to the upper side portion of the first thick wall portion and connects the support portion and the fixing portion. The second thick wall portion constitutes a part of the upper housing and forms the space portion for the pair of balance shafts inside, and a lower surface thereof is formed as a joint surface to be matched with an upper surface of the lower housing.

4. The balancing device for an internal combustion engine according to claim 3, characterized in that: A portion of the first thick wall portion protrudes downward toward the lower case side beyond a joining surface between the upper case and the lower case.

5. The balancing device for an internal combustion engine according to claim 1, characterized in that: The idler shaft has an external threaded portion on the outer periphery of the one end portion in the axial direction. In a state where one end portion of the idler shaft is inserted into a through hole formed inside the support portion, a nut is fastened to the external thread portion, and the idler shaft is fixed to the support portion. The first thick wall portion is provided at a position avoiding the nut.

6. The balancing device for an internal combustion engine according to claim 5, characterized in that: The continuous outer surface of the first thick wall portion and the second thick wall portion is formed in an arc concave shape avoiding the nut.

7. The balancing device for an internal combustion engine according to claim 1, characterized in that: The balance housing and the support portion are formed of an aluminum material, and the first thick wall portion is also formed of the same aluminum material as the balance housing.

8. The balancing device for an internal combustion engine according to claim 1, characterized in that: The first thick wall portion is arranged parallel to an imaginary line that is perpendicular to the mounting surface of the fixing portion and passes through the axis of the idler shaft.

Images